While battling the destructive Waldo Canyon fire in the woods west of Colorado Springs earlier this summer, firefighters stumbled across a large-scale marijuana garden, federal officials revealed Tuesday.

The garden spanned 22 acres on national forest land and included roughly 7,500 marijuana plants, according to a news release. Some of the plants burned in the fire, which torched 18,247 acres and destroyed 346 homes. Investigators removed the remainder of the plants.

The release did not disclose the location of the marijuana garden within the fire’s perimeter. It is not believed to be connected to the fire’s origin.

The revelation about the marijuana patch came as federal officials in Colorado announced their participation in a national effort called Operation Mountain Sweep, which aims to uproot illegal marijuana-growing on public land.

“Use of the public lands for marijuana cultivation is an environmental crime as well as a violation of our nation’s anti-drug laws,” Colorado U.S. Attorney John Walsh said in a statement. “Those who engage in this activity are endangering public safety and harming Colorado’s treasured wild lands and high country, and will be apprehended and prosecuted to the full extent of the law.”

So far this year in Colorado, federal investigators have seized 1,400 marijuana plants growing on federal lands and also confiscated 103 pounds of processed marijuana and more than $350,000 in cash. Earlier this month, authorities in Pueblo County swarmed one of the largest marijuana gardens ever found on public land in Colorado. The Pueblo County Sheriff’s office announced that raid netted more than 13,000 plants.

“The Forest Service is aggressively and decisively combating this issue because public safety is our top priority,” Forest Service Chief Tom Tidwell said in a statement. “While only a fraction of the National Forest system is affected by this illegal activity, our intent is to provide for the safety of all visitors on our lands.”

Illicit marijuana growers on federal lands often leave behind trash and plastic tubing, siphon water from streams and pollute watersheds with fertilizers and pesticides. According to a separate Forest Service news release, it can cost as much as $15,000 per acre to return woodland used to grow marijuana to its natural state.

John Ingold: 303-954-1068, jingold@denverpost.com or twitter.com/john_ingold

You know it’s cold when Mickey won’t ice skate with kids, or when Russian ballerinas have bus trouble. Even some criminals took the day off when Denver’s temperature plunged to minus-10 early Thursday.